Metallocene compounds of transition metals are used as catalyst precursors for polymerization and copolymerization of ethylene and in the stereospecific polymerization of olefins. Metallocenes can be described by the empirical formula (CP.sub.m MLB.sup.1).sub.n (R.sup.2).sub.p. These compounds in combination with an alumoxane such as methylalumoxane (MAO) have been used to produce olefin polymers and copolymers, such as ethylene and propylene homopolymers, ethylene-butene and ethylene-hexene copolymers, e.g., see Kaminsky et al, U.S. Pat. No. 4,542,199 and Sinn et al, U.S. Pat. No. 4,404,344.
MAO has been used as a co-catalyst with various metallocenes. It comprises mixtures of oligomeric linear and/or cyclic alumoxanes with an average molecular weight of about 1200 represented by the formulas: R--(Al(R)--O).sub.n --AlR.sub.2 for linear alumoxanes and (--Al(R)--O--).sub.m for cyclic alumoxanes wherein n is 1-40, m is 3-40, and R is preferably methyl.
Use of MAO has presented problems in the development of catalysts formed from metallocenes. Because of the varying chemical makeup of the material itself, as reflected by its its formula above, it is often difficult to obtain reproducable catalyst synthesis results. If supported catalysts are prepared with combinations of metallocenes and MAO, MAO is not uniformly distributed within catalyst particles. The resulting non-homogeneous polymerization catalysts have low activity and produce resins with less attractive properties.